In many data and telecommunications rack systems, the equipment installed within the rack must be provided with adequate cooling air to ensure proper operation of the equipment. In some cases, heat emanating from adjacent or nearby equipment can interfere with the cooling of other equipment. Also, some racks are configured such that cooling air is provided from the front side of the rack and ejected to the back side of the rack. In the case of equipment that has a bottom inlet for cooling air, it is therefore desirable to guide the air from the front of the rack into the bottom inlet, and to block airflow from the rear of the rack. While systems have been developed to achieve this purpose, improvements are desired, particularly with regard to structural integrity and adjustability.